This commit adds support for using `gke-exec-auth-plugin` (vTPM-based
certificates for mTLS) for webhooks when calling endpoints matching
`*.googleapis.com`, and integrates this support with
ValidatingAdmissionWebhook.
To enable it, request ValidatingAdmissionWebhook with
`ADMISSION_CONTROL=...,ValidatingAdmissionWebhook,...` (default) and
opt in to `gke-exec-auth-plugin` using `WEBHOOK_GKE_EXEC_AUTH=true`
during the configuration process.
If you don't opt-in, ValidatingAdmissionWebhook will be deployed as
before.
Requesting `WEBHOOK_GKE_EXEC_AUTH=true` will fail if you have not
provided other configuration variables:
* `EXEC_AUTH_PLUGIN_URL`: controls whether `gke-exec-auth-plugin` is
downloaded during the installation step. A prerequisite for
actually using the plugin.
* `TOKEN_URL`, `TOKEN_BODY`, and `TOKEN_BODY_UNQUOTED`:
configuration values used when calling the plugin. `TOKEN_URL`
and `TOKEN_BODY` have existing usage. `TOKEN_BODY_UNQUOTED` is a
new variable that is meant to sidestep the problem of inverting
`strconv.Quote` in Bash.
The existing configuration process for ImagePolicyWebhook has been
reworked to make it play nicely with ValidatingAdmissionWebhook under
`WEBHOOK_GKE_EXEC_AUTH=true`.
* It originally placed the ImagePolicyWebhook configuration object
at the top-level of the file specified by
`--admission-control-config-file`. I can't see why this worked;
it must have been hitting some sort of lucky path through the
various config file loading mechanisms. Now, it places its
configuration in a sub-field of that file, which is shared among
all admission control plugins.
* It mounted its various config files read-write. I reviewed the
code and couldn't see why it was necessary, so I moved the config
files into the existing read-only mount at `/etc/srv/kubernetes`.
* It now checks that all the configuration values it requires have
been provided.
Co-authored-by: Mike Danese <mikedanese@google.com>
Co-authored-by: Taahir Ahmed <taahm@google.com>
using `local -r` will blow up, example output:
```
/home/kubernetes/bin/configure.sh: line 388: local: manifest_name: readonly variable
```
Change-Id: Id379180803d44dd9c7ac0da41c1cd56de0fe54a4
The feature caused tests to fail when it was enabled.
- https://github.com/kubernetes/kubernetes/issues/78628
Work is in progress to fix the feature, but until that work is complete,
we will disable it in the GCE scripts.
